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quote:as soon as we run out of fossil fuels, or stop using them, the temperature will begin to catastrophically drop. We have, remaining to us, 120 years, at best, left on this planet.
quote:Originally posted by crandlesRuddimann's view of pre-industrial global warming is a minority opinion. See http://en.wikipedia.org/wiki/Global_warmingThe more majority opinion is that the current interglacial was meant to be a long one so it wasn't supposed to have ended yet.
quote:CO2 levels are likely to stay at elevated levels for thousands of years after we stop using fossil fuels and I doubt we will have a sudden dramatic ceasation of use of fossil fuels. Even if that did happen the warmest period would be at least a decade or two later.
quote:Originally posted by another_someonequote:Originally posted by crandlesRuddimann's view of pre-industrial global warming is a minority opinion. See http://en.wikipedia.org/wiki/Global_warmingThe more majority opinion is that the current interglacial was meant to be a long one so it wasn't supposed to have ended yet.What interglacial - we are not in an interglacial - we are still in a trelatively very cold climate in comparison to most of geological time. There has been a slight rise in temperature above the minimum, but we are well short of being in a warm period.quote:CO2 levels are likely to stay at elevated levels for thousands of years after we stop using fossil fuels and I doubt we will have a sudden dramatic ceasation of use of fossil fuels. Even if that did happen the warmest period would be at least a decade or two later.How do you work out such a long period for CO2 recycling - I would have thought that given that even with the raised levels of CO2 in the atmosphere, they are still only a minute proportion of the amount of O2 (all of which is converted from CO2), that it should not take long at all for the any excess CO2 (of the very slight amount we talk about) to also be converted to O2.Even the web site you quote (which certainly does not look like it is trying to underplay the impact of global warming) only talks abot 50 to 200 years to recycle the CO2, and I personally would be surprised if it took as long as that (although I claim no expertise for behind that opinion).George
quote:Originally posted by crandles>What interglacial? We are at the left hand side of http://en.wikipedia.org/wiki/Image:Ice_Age_Temperature.pngSo we are warmer than most of the last 450,000 years.
quote:An ice age is a period of long-term downturn in the temperature of Earth's climate, resulting in an expansion of the continental ice sheets, polar ice sheets and mountain glaciers ("glaciation"). Glaciologically, ice age is often used to mean a period of ice sheets in the northern and southern hemispheres; by this definition we are still in an ice age (because the Greenland and Antarctic ice sheets still exist). More colloquially, when speaking of the last few million years, ice age is used to refer to colder periods with extensive ice sheets over the North American and Eurasian continents: in this sense, the last ice age ended about 10,000 years ago. This article will use the term ice age in the former, glaciological, sense; and use the term glacial periods for colder periods during ice ages and interglacial for the warmer periods.Many glacial periods have occurred during the last few million years, initially at 40,000-year frequency but more recently at 100,000-year frequencies. These are the best studied. There have been four major ice ages in the further past.
quote:Originally posted by crandlesIf you go back more than 5 million years http://en.wikipedia.org/wiki/Geologic_temperature_recordyes we are colder than most of geologic time but I think the last 450,000 years is more relevant than what happened over 5 million years ago.
quote:The earliest hypothesized ice age is believed to have occurred around 2.7 to 2.3 billion (109) years ago during the early Proterozoic Age.The earliest well-documented ice age, and probably the most severe of the last 1 billion years, occurred from 800 to 600 million years ago (the Cryogenian period) and it has been suggested that it produced a Snowball Earth in which permanent sea ice extended to or very near the equator. It has been suggested that the end of this ice age was responsible for the subsequent Cambrian Explosion, though this theory is recent and controversial.A minor ice age occurred from 460 to 430 million years ago, during the Late Ordovician Period.There were extensive polar ice caps at intervals from 350 to 260 million years ago, during the Carboniferous and early Permian Periods, associated with the Karoo Ice Age.The present ice age began 40 million years ago with the growth of an ice sheet in Antarctica, but intensified during the Pleistocene (starting around 3 million years ago) with the spread of ice sheets in the Northern Hemisphere. Since then, the world has seen cycles of glaciation with ice sheets advancing and retreating on 40,000 and 100,000 year time scales. The last glacial period ended about 10,000 years ago.
quote:Originally posted by crandles>How do you work out such a long period for CO2 recyclingTry http://www.realclimate.org/index.php/archives/2005/03/how-long-will-global-warming-last/A couple of hundred years is a typical lifetime estimate. However there is a small proportion that takes a long time to disappear.
quote:Thus land-based plant sequestration should not be regarded as permanent.
quote:Originally posted by crandlesNot sure what wasn't completely true :?
quote:I disagree that it is ignoring photosynthesis. It just happens to be not very relevant. At equilibrium plant photosynthesis is matched by plant decay, animal respiration and soil decomposition. If you add a slug of new CO2 to the atmosphere, for a brief period the land takes up more carbon. However the amount of carbon that can be taken up by land is limited and a new equilibrium will be reached. This is small compared with the ocean uptake. Between land and ocean around 75% is taken up in a short period of a few hundred years. The remaining 25% takes much longer.
quote:I don't see why you have to ask where the oxygen comes from. The oxygen in the atmosphere is a massive store that represents millions of years of turnover from O2 to CO2 and back. The turnover isn't important it is the net balance. It isn't the O2 we are interested in it is the carbon.
quote:A balance is only something we can ignore if we understand how that balance in maintained, and how it changes.
quote:If humans are creating lots of CO2 through combustion, then they must in fact be using up lots of O2. If you then make the assertion that O2 and CO2 are in permanent balance, then it must follow that there is a process where the O2 that the humans have used is somehow replenished
quote:The absorption of CO2 by the oceans and by carbonate rocks does little to maintain the balance between O2 and CO2 (the processes are happening without regard to the levels of O2 in the atmosphere, excepting insofar as you may judge that in the extreme, an anoxic environment would not support shellfish and other living forms that convert CO2 to carbonates).
quote:It has to be remembered that the only significant means of creating free oxygen on this planet is through photosynthesis, and so one must see the creation of free oxygen as a direct measure of the rate of photosynthesis, and the amount of free oxygen on the planet as a store of historic CO2 that has been converted to O2. Clearly, the turnover is critical in any assessment of the pricess, since it indicates how responsive the system may be to environmental changes.
quote:Originally posted by crandlesquote:If humans are creating lots of CO2 through combustion, then they must in fact be using up lots of O2. If you then make the assertion that O2 and CO2 are in permanent balance, then it must follow that there is a process where the O2 that the humans have used is somehow replenishedWhy would anyone make that assertion? We are trying to see what happens to CO2 so assuming a permanent balance seems very odd. If the O2 stock was changing significantly maybe that would have an effect on the processes of O2 to CO2 and CO2 to O2. However the stock of O2 is so hugeit is changing but not changing significantly.quote:The absorption of CO2 by the oceans and by carbonate rocks does little to maintain the balance between O2 and CO2 (the processes are happening without regard to the levels of O2 in the atmosphere, excepting insofar as you may judge that in the extreme, an anoxic environment would not support shellfish and other living forms that convert CO2 to carbonates). As O2 is not in balance but staying practically constant, any change in ratio of CO2 to O2 is due to changes in CO2. If ocean absorbtion is taking up 75% of the extra CO2 we are producing, how do you decide that is doing "little to maintain the balance"?I still don't see the relevance of O2.
quote:Originally posted by science_guyquote:CO2 levels are likely to stay at elevated levels for thousands of years after we stop using fossil fuels and I doubt we will have a sudden dramatic ceasation of use of fossil fuels. Even if that did happen the warmest period would be at least a decade or two later.part of the reason the temperature will drop is because of the lack of heat from the combustion of fossil fuels. The reactions do produce heat, and that is part of what has kept this planet warm. Without that, the temperature will fall, because the orbit that alters the earth enough to cause the ice age, is well into the cycle and it will not have the immediate benifit of hot sun.
quote:Originally posted by another_someoneI shall be brief, but merely try and clarify the following point:Atmospheric O2 is 209,460 ppmv Atmospheric CO2 is 381 ppmv If 0.18% of the O2 in the atmosphere is converted to CO2, that is a 100% rise in CO2. If all of the CO2 in the atmosphere were to be converted to O2, it would only represent 0.18% change in the volume of O2 in the atmosphere.Are we sure that the volume of O2 in the atmosphere has remained constant to within 0.1% (i.e. less that 1 part per thousand change in total volume, or more accurately, in the number of moles, since volume can also vary because of changes in temperature and pressure) tolerance over geological time (or even within recent times)?George
quote:Originally posted by science_guythe orbit cycles are entirely my point. The orbit cycle started to enter the ice age at b.c. 3000. That means the orbit has had 5000 years to change. Sure the burning of fossil fuels is negligible, but even negligible amounts can add up to be a dominating resource. The point is that humans will no longer be able to survive on the planet for very much long, regardless of how it happens.
quote:Originally posted by crandlesWhy do we want to be sure that the moles of O2 has remained constant to with .1%? That would hardly have much effect on CO2 to O2 or on O2 to CO2. If it was varying more than .1% what would that mean? Well it would probably be to do with other reactions other than the O2 to CO2 and CO2 to O2 reaction. Why? because we know CO2 has not changed by 50% or more recently.So what has this got to do with what we are discussing?
quote:While I accept that the simple argument that forests will convert CO2 to O2 is simplistic, because forests are a complex environment that is generally carbon neutral; but equally, one has to ask where did the oxygen come from
quote:Originally posted by crandlesI am no nearer to understanding why 'one has to ask where did the oxygen come from'.I think these numbers could be a little out of date. I think human fossil fuel use was 7GT several years ago so 5.5 looks a little on the low side. Despite this, I think we understand the processes well enough to make intelligent estimates of how the numbers will change as the CO2 level increases. Models suggest that the carbon in vegetation has been increasing but is likely to soon start decreasing.If the best way of measuring the CO2 level is from ice cores then I don't see why you have to bother with an non optimal method of trying to measure the O2 level or worrying about where the O2 comes from.
quote:Originally posted by another_someoneI, on the other hand, do not understand exactly what the image is trying to say (that a picture says a thousand words does not mean that the thousand words actually make any sense).How, in that picture, would you extract a total figure for all of the CO2 that is converted to O2 through photosynthesis (maybe I am just not looking at the right bot to see the number, and am simply being a total fool, but I cannot see the number).What are the margins of error for these figures?George
quote:Originally posted by crandlesThe figure for photosynthesis is 121.3. That figure is for the carbon cycle and the units are Gigatonnes of carbon per year. To convert to weight of CO2 you would multiply by 44/12.
quote:A reason I introduced the pic was to show the different timescales involved. For carbon in the atmosphere only lasts 750/(121.3+.5+90) = 3.5 years.
quote:A similar calculation can be done for oxygen and I now think it looks like about 10,000 years (not millions as I said earlier sorry).
quote:Originally posted by another_someoneI see where the figure of 121.3 is shown, but is that total photosynthesis. The image seems to indicate the number of gigatonnes absorbed by trees. It is not even clear if that is the figure including all land plants (grasses, mosses, etc.), let alone marine vegetation (including algae).
quote:Do I understand from this statement that within 3.5 years all of the CO2 in the atmosphere (at present levels) will be turned over (i.e. mostly converted to O2, or to carbonates, or to carbonic acid) ?
quote:Given the much greater amount of O2 in the atmosphere than CO2, I would expect it to take longer to turn over (if that is what your figure is trying to say), although I am surprised if takes almost 3000 times as long to turn over 550 times as much O2 as there is CO2. You may suggest that this indicates that only 18% of the CO2 cycle actually is part of the O2 cycle, and thus 82% of the CO2 cycle would be through other pathways, but I will need convincing that these figures are complete enough to make this claim. How are these lifetimes measured?Nonetheless, even if the photosynthesis path only accounts for 18% of CO2 in the atmosphere, it cannot be ignored as insignificant, even if it is the lesser proportion. Since the figures seem to suggest that human input of carbon into the atmosphere amounts to only 0.7% of the carbon already in the atmosphere (even if that figure is slightly higher now, it has not changed by orders of magnitude), the 18% of turnover that is caused by photosynthesis can be enough that a slight change in that figure can have a sufficient impact to absorb the output created by humans.
quote:Originally posted by crandlesDepends what you mean by all. If you really mean 'all' then no lots persists for decades. If by all you mean the same total amount then yes. Clearly some is turned over a few times within 3.5 years and lots are not removed within 3.5 years.
quote:quote:Originally posted by another_someoneGiven the much greater amount of O2 in the atmosphere than CO2, I would expect it to take longer to turn over (if that is what your figure is trying to say), although I am surprised if takes almost 3000 times as long to turn over 550 times as much O2 as there is CO2.Not sure where your 550 came from. 20% of the atmosphere compared to 380ppm is a ratio of around 50,000 not 550. Then you have got to mess about with the weight per volume/mole. My 10,000 could easily be wrong again.
quote:Originally posted by another_someoneGiven the much greater amount of O2 in the atmosphere than CO2, I would expect it to take longer to turn over (if that is what your figure is trying to say), although I am surprised if takes almost 3000 times as long to turn over 550 times as much O2 as there is CO2.
quote:That 0.7% figure you mentioned (5.5/750) is the amount per year not in total. The CO2 level is 30% higher as you mentioned earlier.
quote:For better figures we are putting 7gigatonnes of carbon into the atmosphere but when we measure the atmosphere only 4 gigatonnes is turning up. So there is a natural reaction of the system to try to restore the balance by absorbing 3gigatones.
quote: Yes 'a slight change in [photosynethis] could have a sufficient impact to absorb the output created by humans'. However, it doesn't look likely - why hasn't it happened so far? A more reasonable interpretation is that the natural reaction is only 3 gigatonnes and we are currently overwhelming this with 7 gigatonnes of carbon. It may seem reasonable to suggest that the 3GT could grow as we move more than 30% above CO2 levels of 100 years ago, but there are suggestions that the land will become a net emitter soon. There are also limits to ocean absorbtion - how much can be absorbed before the buffering ability of the ocean is exhausted and it start to become more acidic more rapidly?
quote:I recognise the 0.7% was annual anthropogenic input; on the other hand, the 30% is not proven to be anthropogenic, or to what extent it may be anthropogenic.Are you not jumping to conclusions?Yes, we can say that we can measure 7 gigatonnes going in, and only 4 gigatonnes remaining in; but what can we say about how much would have been there if we had not put 7 gigatonnes in – we can say nothing.We cannot say whether, if we had not pumped 7 gigatonnes of carbon into the atmosphere, the atmosphere may have actually had a reduction of 3 gigatonnes over what it had before; or whether if would have had an increase of 4 gigatonnes anyway, whether or not we had pumped the 7 gigatonnes in.
quote:then what other factors may alter the balance point that effects this sensitivity?
quote:If the issue is that the environmental system had enough slack to exactly absorb 3 gigatonnes of carbon in CO2 per year, and no more; it would seem a remarkably (to my view) unlikely scenario – why exactly 3 gigatonnes? If it had just so much slack, then what we should see in the records is that each year, up until the point where human output exceeded 3 gigatonnes of carbon in CO2 there should have been zero increase in global CO2 levels, and each year subsequent to that point, we should have seen each tonne of additional anthropogenic CO2 reflected by exactly 1 tonne of additional CO2 in the atmosphere. I am not aware that this is what has been observed.
quote:Originally posted by crandlesIt is true that for a single year, we wouldn't know if new sources or sinks to the tune of 7 gigatonnes had just arisen.
quote:However, we have record of CO2 from ice cores going back hundreds of thousands of years. From this we know that the changes we are seeing now: A change from 300 to 380ppmv (~180gigatonnes)within 100 years is extremely unusual.
quote:It makes sense for the natural reaction to such a large change to be that the land and ocean to take up carbon. So it is possible for new sources or sink to have arisen to the tune of 180 gigatonnes, but for this to have happened at just the right time would be a really remarkable coincidence.Some likely ways the system will respond:*If the CO2 in atmosphere increase the amount of CO2 being dissolved by the oceans will increase (and CO2 releassed decrease) until the balance is restored.*Extra CO2 in atmosphere will cause increase in photosynethis as one of the imputs has been increased. However there are limits to how long this can last for as there is a limit to the amount of carbon that can be put into vegetation. At some point that increase in vegetation starts to die off and rot.So we would expect the processes to be sensitive to the amount of CO2 and possibly ratio to other gasses.
quote:I would expect that the amount has grown to 3gigatonnes per year slowly as the CO2 level has risen and the CO2 record is consistent with this. This is why I said "It may seem reasonable to suggest that the 3GT could grow as we move more than 30% above CO2 levels of 100 years ago"I have pointed out why there are limits to the growth of that 3GT. I certainly don't think it is 'exactly 3 GT and no more'. Given the arguments for a limit to the growth of the 3GT I think it is foolishly optimistic to expect that 3GT to keep on growing so that we don't need to cut carbon emissions.
quote:Originally posted by another_someonequote:Originally posted by crandlesIt is true that for a single year, we wouldn't know if new sources or sinks to the tune of 7 gigatonnes had just arisen.The issue is not whether a new source or sink had arisen, but how much variability exists within the existing sources and sinks.
quote:quote:However, we have record of CO2 from ice cores going back hundreds of thousands of years. From this we know that the changes we are seeing now: A change from 300 to 380ppmv (~180gigatonnes)within 100 years is extremely unusual.While I am not saying that you are wrong, would you like to be more explicit. Exactly how unusual? How precise are our long term historic measurements? Can we say that over a 60 million years or more that we know with precision exactly what happened from one century to the next (in fact, as far as I can see, most of our more precise data is over less than ½ million year period, a very short period over the history of the Earth, and it is not clear to me that even over that period we have the kind of precision that would tell us what was happening within any given century)?
quote:Throughout most of the record, the largest changes can be related to glacial/interglacial cycles within the current ice age.
quote:Direct solution into the oceans is unlikely to really provide an adequate response, particularly since any warming influence (whether as a consequence of greenhouse gases, or as a consequence of increased solar input – the latter of which we know we have been experiencing in recent centuries – would actually cause less CO2 to be dissolved into the oceans).The real issue has to be, to my mind, around how vegetation (including single celled photosynthesising organisms) respond. As you say, after a while these organisms will die, but what happens to them when they die?Forests are fairly hopeless as sinks because they do indeed either get quickly eaten by bacteria, fungi, or animals. Peat bogs are certainly better, since they are anaerobic and will not convert back to CO2. The question then has to be what happens within the oceans? If the dead vegetation can reach anaerobic conditions (i.e. fall into the depths of the ocean), then it is still possible they can avoid being converted back to CO2. Similarly, if the about of animals that create carbonate shells increases, and these then fall to the depths, then that will remove carbon from the system.All of the above do not assume any increase in photosynthesis, but simply a change in the context of the photosynthesis, and a reduction in the processes that convert the carbon back to CO2. This may even happen simply because of the death of many organisms that would generate CO2 (e.g. a reduction in the number of plant eating animals). It is certainly true that as humans grow vegetation for their own purposes, they do deliberately try and prevent other wildlife from consuming it (unlike when humans create forests and nature reserves, where they deliberately encourage wild life to eat the vegetation).
quote:Originally posted by VAlibrarianBut really, most women in the third world would be thrilled to have fewer children.
quote:Originally posted by VAlibrarianI have to point out that 95% of climatologists agree with Crandles on this issue. We are not in any immediate danger of an ice age, but we are in immediate (100 to 200 years) danger of melting the Greenland and Antarctica ice sheets and saying goodbye to Bangladesh and part of Florida.
quote: Why would you assume that eventually doubling the amount of CO2 in the atmosphere would somehow improve the world climate?
quote:I get baffled by you guys after a while. I am forced to conclude that you have made a decision to disagree with the prevailing conclusion on global warming because you do not like to agree with a scientific consensus. Why is that? Clearly it is not due to religious convictions. Maybe you enjoy feeling superior, and agreeing with others does not provide you that feeling? I am sorry if this sounds a bit personal. But really, they pay these climatologists to figure things out. Why do you think you know science better than they do?
quote:Originally posted by another_someoneThis is the difference between us that you seem to find so difficult to comprehend – that I do not believe that in the grand scheme of things there can ever be in any absolute sense 'good' or 'bad', or 'better' or 'worse' climate. Good and bad are ethical judgements, and how do you make ethical judgements about climate? Climate is as it is, and it has never stood still, so why should it now?Was the mini-ice age in the middle of the 17th a better or a worse climate than we have today? Was the medieval warm period that preceded it a better or worse climate than that of the mini ice age?Do you really think that as the climate cooled between the 11th to the 17th century, people did not suffer; or that as the climate warmed since then, that people did not suffer? Do you really believe we can ever create a world where the climate does not change, or where that change will not present challenges?
quote:Originally posted by crandlesDo you really think that we cannot make judgements like a fast rate of change is worse than a slow rate of change?
quote:The extinction of any species by our hands is a crime beyond all other crimes
quote:Originally posted by crandlesI think that is just weird (and I say that to try to keep within the limits of what I can say to a moderator). There are lots of things that are clearly bad about a fast rate of change.The opening post also saidquote:The extinction of any species by our hands is a crime beyond all other crimesTo take things to the extreme, I don't think it is hard to say we don't want a process like: global warming >> ocean anoxia >> H2S outgassing process >> Ozone destructionand each/each combination resulting in mass extinctions.See http://www.sciam.com/article.cfm?chanID=sa006&articleID=00037A5D-A938-150E-A93883414B7F0000&pageNumber=1&catID=2
quote:Originally posted by another_someoneThere is a difference between saying you don't want something, and saying that it is in some absolute sense 'bad'. All I said was that one cannot talk in absolute terms about 'good' or 'bad', but only in relative terms by saying that you desire a particular outcome, and something will help or hinder that outcome. I was merely arguing against the unqualified use of the terms 'worse' or 'better', in that you did not say what the objective was that you felt these things were better or worse for, thus making it difficult to agree or disagree as to whether it would be better or worse for such an outcome.
quote:One interesting aspect of the article is that it seems to make very different assumptions to the ones you have made earlier. The article uses C12/C13 atmospheric ratios as an indication of the amount of photosynthesis – the assumption being that there is a constant amount of carbon that is shared between living organisms and the atmosphere, and thus the less C12 in relation to C13 in the atmosphere can be regarded as a direct measure of the amount of C12 taken up by living organisms. This seems to contradict your earlier argument that the amount of carbon taken out of the atmosphere by photosynthesis is negligible, and that the dominant means of extracting carbon from the atmosphere is inorganic (which would affect the C12/C13 ratios differently and would likely confuse any measurement that ignored those factors).
quote:What is also interesting (as you have yourself now mention) is the issue of anoxia – but this again contradicts your earlier insistence that we can ignore the oxygen levels in the atmosphere as telling us nothing useful regarding the carbon cycle (on the assumption that most of the carbon cycle had little to do with photosynthesis). Then again, if O2 levels dropped so far as to allow anaerobic life to exist in most of the ocean, then we are talking about levels of CO2 that would be well above the most extreme that anyone has talked of coming about from industrial output (in fact, humans would be incapable of pushing CO2 levels to that extreme since the lack of atmospheric oxygen would make combustion extremely difficult, aside from the requirements for humans themselves).
quote:In fact, as far as I can see, the scenario the article is talking about came about not so much directly by the increase of CO2, as by the reduction of O2 that allowed the growth of anaerobic bacteria.
quote:Of course, you might argue that the other factor that would have an effect is global warming (not CO2 necessarily, but any cause that would increase water temperatures). The only thing to be said about that is that even with the present climate being warmer than any time since the middle ages, it is still very much cooler than at many other times when mass extinctions did not take place.
quote:In any case, if one's main concern is the H2S that may be produced by anaerobic bacteria in the ocean, this could be addressed directly by seeking to control the growth of that bacteria in other ways (although the assumption seems to be that this would at most be only a threat some centuries hence, and direct intervention could be very much faster and more manageable that trying to manipulate atmospheric O2 and CO2 levels).
quote:Originally posted by crandlesThere is a difference between absolute and relative but in this case it is so obvious as to not really make any practical difference.
quote:Different techniques for different purposes and even different time periods can be appropriate.Earlier we wanted to compare the 7 gigatonnes of carbon from fossil fuels to the net difference 121.3+.5-60-60-1.6=0.2 For this we didn't really care much what the 121.3 figure was exactly because there was more uncertainty in the 60 figures. We only wanted the change in the level of carbon in soil and vegetation and to consider how that was likely to change with time.If you do want to know the 121.8 figure then using the C12/C13 ratio is appropriate.
quote:Not really sure where I was insisting we can ignore the oxygen levels but it is quite possible I have said something either to that effect or has been misinterpreted. If you can go about measuring something in at least two different ways, then it can be sensible to use the method with a low margin of error (measuring the carbon)rather than a method with a high margin of error(measuring the oxygen). This is not the same as saying ignore the oxygen level for all purposes!
quote:Trying to slip in 'warmer than any time since the middle ages'? There are lots of reconstructions and their best estimates all show a temperature for the medieval warm period cooler than today.
quote:I did say it was an extreme when I introduced it. I felt it showed that it was easy to say a fast rate of change was bad and this was so self evident that it didn't need an excercise in deciding what was bad.
quote:As researchers continued to probe the data in recent years, however, they found that some things did not add up. New fossil analyses indicated that the Permian and Triassic extinctions were drawn-out processes spanning hundreds of thousands of years. And newly obtained evidence of the rise and fall of atmospheric carbon, known as carbon cycling, also seemed to suggest that the biosphere suffered a long-running series of environmental insults rather than a single, catastrophic strike.
Dispute continues over Michael Mann’s “hockey stick” graph, which purports to prove that the last 25 years have been the warmest in the last 1,000 years. Scientists have shown that a key step in the process used to generate Mann's graph is strongly biased in favour of finding hockey stick patterns even in lists of random numbers. One internationally renowned expert has called the graph “methodologically wrong” and “rubbish.”July 2004 was the coolest July in the last four years. Perhaps that’s partly because the annual rate of increase in the concentration of CO2 in the atmosphere is only about half of what is expected based on man-made emissions. Scientists believe the oceans are absorbing the missing half.The arctic today, though warmer than it was in 1970, is colder than it was in 1930. In fact, temperatures in Greenland have fallen over the last 15 years. That is leading some scientists to believe that shifts in the wind, rather than temperature change, are responsible for any retreating of the arctic ice.It is hard to settle on a results-oriented metric for what is happening with climate change in the United States or around the world. And it’s even harder to settle on one for the ongoing dispute about policy responses.The best metric would be temperature. Everyone agrees that global temperatures have risen about 0.6 degrees celsius over the last century.1 But controversy remains about the accuracy of our recent measurements and the pace of warming. In 2004, there were more attempts to square one of the leading anomalies of climate measurement.Ground-based temperature readings show a warming trend over the last 25 years. Satellite temperature measurements of the lower atmosphere (or troposphere) show only about half as much warming, even though most climate models suggest the lower atmosphere should warm even more than ground level. To understand this controversy, keep in mind that ground-level temperatures are taken the old fashioned way—with thermometers. They are then corrected for the “urban heat island effect,” i.e. the fact that most temperature readings are taken near cities and other human-altered areas where temperatures are higher than the average atmospheric temperatures for the planet as a whole.Satellite temperature readings, by contrast, come from microwave readings rather than direct measurement. They require statistical interpretation because microwave readings yield different temperatures at varying elevations from the earth’s surface. Any data that can be interpreted statistically can be re-interpreted statistically to get a different result. This is exactly what a team led by Qiang Fu at the University of Washington did in a study published in Nature last May.2By “correcting” for the cooling effect of the stratosphere (the next layer of the atmosphere above the troposphere), the satellite results can be brought into line with the surface thermometer readings. Case closed? Probably not. John Christy, director of the Earth System Science Center at the University of Alabama/Huntsville, disputes the Fu findings, and argues that the Fu team has over-corrected for stratospheric cooling and introduced new statistical errors into the analysis. Christy was one of the designers of the satellite observation system, and the first to point out, more than a decade ago, the discrepancy between satellite and surface temperature readings.This is not the first attempt to reconcile the clashing temperature findings with statistical re-analysis, and it is unlikely to be the last. Another major statistical controversy over temperature readings erupted during the last two years.As sports-minded readers know, the entire National Hockey League season was called off in 2004 on account of labor difficulties. While it is certainly coincidental, we can’t help but notice that the famous “hockey stick” graph that was supposed to be the “smoking gun” of global warming has quit working too. The dispute about Michael Mann’s “hockey stick” graph, which purports to prove that the last 25 years have been the warmest in the last 1,000 years, has intensified in recent months. Criticisms are rolling in from more scientists and statisticians. As reported in last year’s edition, the Mann “hockey stick” graph would seem to negate what has always been referred to as the “medieval warm period” that preceded the “little ice age,” from roughly 1400 to 1850. New statistical critiques from Steven McIntyre and Ross McKitrick, the duo that raised the first questions about the hockey stick, have furthered doubts about the accuracy of the hockey stick. Other climate scientists, including several affiliated with the Intergovernmental Panel on Climate Change (IPCC), have reviewed the methodological dispute and come down on McIntyre and McKitrick’s side.McIntyre and McKitrick have demonstrated that the computer algorithm used to generate the hockey stick graph is strongly biased in favor of finding hockey stick patterns even in lists of random numbers. Dr. Rob van Dorland, an IPCC lead author and climate scientist at the Dutch National Meteorological Agency, has said the controversy will “seriously damage the image of the IPCC.” Van Dorland added: “It is strange that the climate reconstruction of Mann passed both peer review rounds of the IPCC without anyone ever really having checked it.”The most devastating critique comes from Hans von Storch, an IPCC contributing author and internationally-renowned expert in climate statistics at the Center for Coastal Research in Geesthacht, Germany. He has said the McIntyre-McKitrick critique is “entirely valid,” and that the hockey stick graph “contains assumptions that are not permissible. Methodologically it is wrong: rubbish.”University of California physicist Richard Muller wrote in Technology Review that the hockey stick “turns out to be an artifact of poor mathematics.” Everyone, including McIntyre and McKitrick, is quick to qualify their criticisms by saying the debunking of the hockey stick does not mean global warming is not happening today; merely that we still cannot confidently tell from the available data the exact temperature history of the last millennium.3This is a vital point, because whenever anomalies call into question our mastery of climate science, the defenders of urgent action immediately repair to the “consensus.” Critics of specific aspects of climate science are usually portrayed—if not demonized—as climate change “skeptics” or deniers, on par with Holocaust deniers.Science magazine stirred a furor late in the year with “The Scientific Consensus on Climate Change,”4 an article by Naomi Oreskes. She analyzed nearly 1,000 articles on climate science in scientific journals, and found none dissented from the “consensus” position. Oreskes concludes that “there is a scientific consensus on the reality of anthropogenic climate change. Climate scientists have repeatedly tried to make this clear. It is time for the rest of us to listen.”Roger Pielke of the University of Colorado pointed out on his website that Oreskes’s argument amounts to a poorly constructed straw man.5 Who, exactly, says the general consensus is wrong? Fred Singer, considered one of the leading “skeptics,” says: “In fact, the IPCC statement is in many ways a truism. There certainly must be a human influence on some features of the climate, locally if not globally.” Another leading “skeptic,” Pat Michaels, says: “It has been known since 1872 that water vapor and carbon dioxide are the principal ‘greenhouse’ gases in the atmosphere, and that increasing their concentration should elevate the temperature in the lower atmosphere. What has been a subject of contention ever since is the amount and character of the warming.” And Bjørn Lomborg has said: “There is no doubt that global warming is happening or that it is important. Carbon dioxide from burning fossil fuels will increase Earth’s temperature. That is likely to have an overall negative effect.”This last statement from Lomborg is especially significant because he has raised the question in acute form of what should be done now about climate change relative to other current world problems. Even Oreskes herself admits that “Many details about climate interactions are not well understood, and there are ample grounds for continued research to provide a better basis for understanding climate dynamics. The question of what to do about climate change is also still open.” (Emphasis added.) Lomborg’s “Copenhagen Consensus” exercise last year ranked global warming low on a list of world priorities, for which he was roundly abused.Dr. Rajendra Pachauri, the IPCC’s chairman, compared Lomborg to Hitler. “What is the difference between Lomborg’s view of humanity and Hitler’s?” Pachauri told a Danish newspaper. “If you were to accept Lomborg’s way of thinking, then maybe what Hitler did was the right thing.” Lomborg’s sin was merely to follow the consensus practice of economists in applying a discount to present costs for future benefits, and comparing the range of outcomes with other world problems alongside climate change.It is hard to judge what is worse: Pachauri’s appalling judgment or his abysmal ignorance of basic economics. In either case, it is hard to have much confidence in the policy advice the IPCC might give. It might be added that when Pachauri compared Lomborg to Hitler, he ran afoul of what is known in the Internet blogosphere as “Godwin’s Law,” which holds that resorting to reductio ad Hitlerum is a sure sign that someone is losing an argument.Are the “skeptical” questions about our mastery of climate science and its relation to the timing of policy very different from some of the caveats that appear in the “consensus” reports, such as the IPCC’s latest assessment? Consider, for example, this passage from the latest IPCC assessment report:There is an increasing realization that natural circulation patterns such as 'El Nino-Southern Oscillation' and 'North Atlantic Oscillation' play a fundamental role in global climate science and its interannual and longer-term variability.6Or this, from a different section of the IPCC report:In climate research and modeling, we should recognize that we are dealing with a coupled non-linear chaotic system, and therefore that the long-term prediction of future climate states is not possible.7To this can be added the judgment of the U.S. National Research Council, from whose 2001 report, “Climate Change Science: An Analysis of Some Key Questions,” one sentence was widely cited by climate-action enthusiasts: “The recent [climate] changes observed over the last several decades are likely mostly due to human activities.”If, as keepers of the “consensus” view readily admit, “the question of what to do about climate change is still open,” then why this belabored attempt to bash a straw man, if not to build political pressure for the agenda of immediate carbon suppression? As the argument over our knowledge of climate science continues to go badly for alarmists, advocates of Kyoto-style carbon suppression are becoming increasingly shrill.